Certain species of game fish prefer to feed below the water's surface at different depths within the water column. For decades, fishermen have employed the use of diving lures that will plane down to a particular depth and attract these types of game fish. The attachment of a fixed diving bill to the front of any shaped diving lure will create a diving plane when the line is attached at a point behind the leading edge of the diving bill and pulled by a boat or cranked with a reel through the water. The water flowing from the front to back of the lure and moving over the diving bill creates downward pressure on the diving bill, causing the lure to dive.
This method becomes significantly less manageable for the fisherman as lure sizes for very large game have increased over time. This phenomenon is pronounced in saltwater fishing where the game fish are exponentially larger than fresh water species and the commonly used fishing lure sizes have grown in size commensurate with their target prey.
Large diving lures with fixed diving bills, sometimes pulled at speeds of 5 to 7 knots, create a tremendous amount of hydrodynamic pressure against the diving bill in order to cause the lure to dive to depths of 25 to 50 feet below the surface. This pressure on the lure diving at these depths when trolled with fishing rods and reels and connected to the fishing line create three very specific problems for the fisherman.                1. The diving fishing lures are very difficult to retrieve by reeling them back to the boat while the boat is still trolling at these speeds. Many times, there is more than one lure being trolled behind the boat, so stopping the boat to more easily retrieve the lure is not a good solution. The other lures and attached fishing lines can become tangled while the boat is stopped.        2. Once an actual game fish has struck the lure and is hooked in some nature on the attached hooks, the fish can use the water pressure on the lure to work itself free of the hook. A direct line to fish connection has the best probability of keeping the hook lodged in the fish's mouth. The water pressure on a fixed diving bill, even while a fish is hooked on one of its hooks, inhibits a direct line to fish connection and can cause the fisherman to lose the fish.        3. The diving lures are sometimes trolled very close to the bottom of the water column, near obstructions and objects on the bottom that are habitat for large game fish and their natural food sources. If the diving lure encounters an obstruction in its path, it will strike it and continue to dive, striking it over and over again, potentially becoming snared by its own hooks on the obstruction.        
In addition to these specific problems, there eventually comes a point where the combination of the size of the lure, and the pressure it generates when trolled behind the boat creates an actual limitation to how far a diving lure can be engineered to dive. It is at this point a diving lure becomes impractical to fish with. The largest diving lures with fixed diving bills available today have essentially reached that limitation.
The present invention art depicts an apparatus built within the diving bill, which allows the diving plane to be eliminated. By eliminating the diving plane with the built-in, spring-loaded, adjustable release apparatus in the diving bill, it solves the three issues created by a fixed diving bill, and helps to solve the broader limitation of how large and how deep a lure can be engineered to dive. The spring-loaded and adjustable features of this apparatus are critical to its operation, since trolling speeds for various species of fish can vary, causing the relative pressure on the lure to vary. The optimal adjusted setting of the present invention apparatus will allow the lure to travel through the water in a diving position, but be released by one of three events:
The fisherman triggers the release through a jerk of the line attached to the lure
A fish strikes the lure and becomes hooked, or
The diving lure strikes structure on the bottom of the water.